Out of the 283 part-time Tufts faculty eligible to vote, 128 voted to join Adjunct Action, a movement backed by the Service Employees International Union; 57 voted against joining and 98 others did not vote. The ballots was tallied Thursday following a two-week mail-in voting process.

Carol Wilkinson, a part-time lecturer who has taught in the English Department at Tufts since 1986, helped lead the campaign. “It’s an issue of wanting to be heard,” she said Friday. “At Tufts, there’s been no way for the part-time faculty to have any say over issues that involve us and the university as a whole.”

The next step for Wilkinson and her colleagues is contract negotiations, with compensation and job security among the main topics.

Kimberly M. Thurler, a spokeswoman for Tufts, said the school supports adjuncts’ right to unionize and “moving forward, we hope to work productively with the SEIU as the collective bargaining process begins.”

Wilkinson agreed that Tufts has respected the process. She said administrators have said they plan to bargain in good faith.

Part-time lecturers at Bentley University began voting last week. Those mail-in ballots are scheduled to be counted Oct. 4. The SEIU said adjuncts at Northeastern University are also moving to unionize, though no vote has been scheduled there.

“Though once a quintessential middle class job, adjuncts have become part of the low-wage workforce,” said a statement from the SEIU, which has unionized more than 15,000 adjunct professors nationwide.

Part-time and non-tenure-track faculty represent a growing majority of faculty at US universities, according to the American Association of University Professors.

In 1975, 30 percent of faculty were employed part time. Today, part-time faculty account for more than half of college teaching jobs, and about 76 percent of higher education instructors hold non-tenure track positions, the association said.

According to the SEIU, among private, nonprofit universities in the Boston area, 67 percent of faculty are non-tenure track and 42 percent are part-time.

The national movement received attention after the recent death of Margaret Mary Vojtko, an adjunct professor who taught for 25 years at Duquesne University in Pittsburgh. Vojtko, who like other adjuncts did not receive health benefits from her employer, reportedly died nearly destitute at age 83 shortly after the university declined to renew her contract.

A lawyer for a union that Duquesne teachers have been trying to join wrote an op-ed piece about Vojtko’s death in the Pittsburgh-Post Gazette, igniting a nationwide debate over the plight of adjuncts.